Optical wavelength optimization for high speed WDM transmission system

Abstract

An optimized optical transmitter for use with a 1.3 μm directly-modulated DFB laser. A negative fiber dispersion is intentionally introduced into the system by selecting the operating wavelength to be less than the nominal zero-dispersion value. The introduction of the negative fiber dispersion reduces the system power penalty and results in an optical transmission system useful over relatively short lengths of standard single mode fiber (50 km, for example) without the need for additional amplification.

What is claimed is: 
     
       1. An optical transmission system including a laser transmitting device and a single mode transmission fiber, said fiber having a nominal zero-dispersion wavelength range of λ 0  ±Δλ, λ 0  being defined as the fiber zero dispersion wavelength and Δλ being defined as a predetermined, known variation of said fiber zero dispersion wavelength, wherein a system wavelength λ sys  exhibits a negative dispersion-related power penalty and is selected from within a system wavelength range of Δλ sys  having an upper bound of λ 0  -Δλ and a lower bound defined by the relation:   lower bound=M(S*L)+(λ.sub.0 +Δλ),     where M is defined as the maximum fiber negative dispersion value for which the dispersion power penalty is negative, S is defined as the dispersion slope of the single mode transmission fiber and L is defined as the transmission length of said single mode transmission fiber.   
     
     
       2. An optical transmission system as defined in claim 1 wherein the transmission length of the single mode fiber is less than or equal to 50 km, having a nominal zero-dispersion wavelength of approximately 1310 nm and an associated Δλ of 20 nm. 
     
     
       3. An optical transmission system as defined in claim 2 wherein the maximum value of the negative fiber dispersion is approximately -600 ps/nm and the dispersion slope is approximately 0.1 ps/nm 2  /km, resulting in a system wavelength range of approximately 1210-1290 nm. 
     
     
       4. An optical transmission system as defined in claim 1 wherein the laser transmitting device comprises a directly-modulated distributed feedback laser.